Wireless frequency bands are crowded, and it becomes a problem how to realize higher transmitting speed with limited frequency band. Different communication systems can be set in one electronic product to improve utility, but the parasitic signal generated by nonlinear characteristic of electronic products can often self-interfere, or cause interference elsewhere. Technicians can use high order filter (such as sixth order filters) to filter interference to solve interference problems in multisystem, but high order filter may result in lower output capability, nor can it solve the self-interference problem. Therefore, a new interference suppression system and method are required.